Understanding the relationships between composition, process, cellular structure and properties of cellular polymers based on blends of polystyrene with inorganic and organic nucleating agents

El objetivo principal de este trabajo consiste en estudiar y entender la relación entre composición, proceso, estructura y propiedades de polímeros celulares en base poliestireno que incorporan nanopartículas inorgánicas (sepiolitas) o partículas orgánicas (SEBS) con la finalidad de reducir la conductividad térmica de los mismos.Departamento de Física de la Materia Condensada, Cristalografía y MineralogíaDoctorado en Físic

Fabricación y caracterización de materiales poliméricos nanocelulares: análisis de las propiedades acústicas cuando el tamaño de celda cambia del rango micrométrico al nanométrico

El estudio realizado pretende, por un lado comprender la fabricación de espumas microcelulares y nanocelulares de polimetilmetacrilato (PMMA) con tamaños adecuados y densidades relativas similares. Por otro lado, este estudio busca mostrar si existen o no diferencias entre las propiedades acústicas cuando el tamaño de celda pasa del rango micrométrico al nanométrico Como resultado, se ha conseguido obtener un conjunto de muestras de distinto tamaño de celda, el cual varía desde los 11 micrómetros hasta los 200 nanómetros aproximadamente, con unas densidades relativas comparables (en torno a 0.5). Cada una de estas muestras fue sometida a una serie de ensayos en los que se midieron diferentes propiedades acústicas. En particular, se midieron el coeficiente de absorción y el coeficiente de transmisión. Se han encontrado unas diferencias significativas entre un tipo de muestras y otras, dependiendo del tamaño de celda que presentasen, tanto en absorción como en transmisión. Este hecho sitúa a las espumas nanocelulares como potenciales candidatos para ser utilizados en aislamiento acústico, sobre todo en aquellos sistemas multifunción. Por otro lado, se necesitan más estudios teóricos y experimentales para este tipo de materiales nanocelulares que permitan entender el comportamiento obtenido.Grado en Físic

Nanoporous PMMA: A novel system with different acoustic properties

The acoustic properties of closed cell nanoporous and microporous poly(methyl methacrylate) (PMMA) foams have been well characterized, showing that nanoporous PMMA exhibit a different absorption coefficient and transmission loss behavior in comparison with microporous PMMA. Experimental differences may be explained by the different wave propagation mechanism in the micro and nanoscale, which is determined by the confinement of both the gas (Knudsen regime) and the solid phases. These results place nanoporous materials as a new class of polymeric porous material with potential properties in the field of acoustics, especially in multifunctional systems requiring a certain degree of soundproofing

Polystyrene/sepiolites nanocomposite foams: Relationship between composition, particle dispersion, extensional rheology, and cellular structure

Producción CientíficaThe main objective of this work is to analyze how the cellular structure of foamed polystyrene based (PS) nanocomposites, produced by gas dissolution foaming, is affected by the extensional rheological behavior of the polymer matrix and by the dispersion degree of the particles. These composites have been produced with different types of natural and organomodified sepiolites and with different contents of these particles. The extensional behavior and the dispersion degree were characterized by extensional and shear dynamic rheology, respectively. The results obtained indicate that the extensional rheological behavior controls the foam degeneration mechanisms; meanwhile, the way in which the particles are dispersed in the PS matrix controls the nucleation mechanisms. Results also indicate that, in these systems, the characteristics of the cellular structure are mainly defined by the way in which nucleation occurs. Therefore, improving the dispersion degree is a key approach to reduce the cell size by 90%, with respect to the pure polymer.Junta de Castilla y León (project VA202P20)Ministerio de Ciencia, Innovación y Universidades (project RTI2018-098749-B-I00

Database of spatial distribution of non indigenous species in Spanish marine waters

Research in marine Spanish waters are focused on several actions to achieve an effectively management on protected areas, with the active participation of the stakeholders and research as basic tools for decision-making. Among these actions, there is one about the knowledge and control on NIS. One of its objectives is the creation of NIS factsheets, which are going to be added to the National Marine Biodiversity Geographical System (GIS) providing complementary information about taxonomic classification, common names, taxonomic synonyms, species illustrations, identification morphological characters, habitat in the native and introduced regions, biological and ecological traits, GenBank DNA sequences, world distribution, first record and evolution in the introduced areas, likely pathways of introduction, effects in the habitats and interaction with native species, and potential management measures to apply. The database will also provide data for (1) the European online platforms, (2) the environmental assessment for the Descriptor 2 (D2-NIS) of the EU Marine Strategy Framework Directive (MSFD), as well as (3) supporting decisions made by stakeholders. It is the result of extensive collaboration among scientist, manager’s and citizen science in the Spanish North-Atlantic, South-Atlantic, Gibraltar Strait-Alboran, Levantine-Balearic and Canary Islands marine divisions, providing an updated overview of the spatial distribution of relevant extended and invasive NIS of recent and established NIS introduced by maritime transport and aquaculture pathways, as well as on cryptogenic or native species in expansion due to the climatic water warming trend

Influence of extrusion process, amount and type of particles on the rheological properties of PS/NANOCLAY nanocomposites

El presente trabajo tiene como principal objetivo la producción y selección de un material, entre un conjunto de ellos, aditivado con partículas de dimensiones nanométricas. Para realizar esta selección se utiliza la reología (tanto de cizalla como extensional) a modo de herramienta predictora. Así mismo se variarán ciertas condiciones, a saber: cantidad de particulas introducidas, tipo de las mismas y condiciones de proceso, para tener un férreo conocimiento de los parametros que afectan al proceso de formación de un material celular aditivado con nano-compuestos. Por último, las formulaciones que presenten mejores resultados reológicos, seran sometidas a un proceso de espumado por disolución de gas. Obteniendo muestras celulares, las cuales, serán caracterizadas estructuralmente mediante microscopía electrónica de barrido.Departamento de Física de la Materia Condensada, Cristalografía y MineralogíaMáster en Nanociencia y Nanotecnología Molecula

Influence of the dispersion of nanoclays on the cellular structure of foams based on polystyrene

Producción CientíficaIn the present work blends of polystyrene (PS) with sepiolites have been pro-duced using a melt extrusion process. The dispersion degree of the sepiolites inthe PS has been analyzed by dynamic shear rheology and X-ray micro-computed tom ography. Sepiolites treated with quaternary ammonium salts(O-QASEP) are better dispersed in the PS matrix than natural sepiolites(N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A perco-lated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEPand 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processeshave a negative effect on the polymer architecture. They produce a reductionin the length of the polymeric chains, and they do not lead to a better disper-sion of the particles in the polymer matrix. Foams have been produced using agas dissolution foaming process, where a strong effect of the dispersion degreeon the cellular structure of the different foams was found. The effects on thecellular structure obtained by using different types of sepiolites, different con-tents of sepiolites and different extrusion conditions have been analyzed. Thefoams produced with the formulations containing O-QASEP present the lowestcell size and the most homogeneous cellular structures.Consejería de Educación, Junta de Castilla y León (Grant/Award Number: VA202P20)Ministerio de Ciencia, Innovación y Universidades (Grant/AwardNumber: RTI2018-098749-B-I0